A Multiple Hurdle Carcass Washing Protocol for Inactivating Shiga Toxin-producing Escherichia coli on Beef

Introduction: Shiga toxin-producing Escherichia coli (STEC) O157:H7 and nonO157 STEC serogroups are important foodborne pathogen affecting beef industry. Cattle hide and gastrointestinal tract are considered the primary source of these pathogens. Beef gets contaminated at the hide removal and evisceration step of the slaughtering process. Effective intervention method is required for lessening the number of STEC related outbreaks in beef.

Purpose: The objective of this study was to develop a multiple hurdle carcass intervention protocol for reducing STEC on beef.

Methods: A 25 cm² area on fat and lean side of subprimal beef cuts was marked and were inoculated with (seven or five log CFU/cm²) five-strain cocktail of nalidixic acid resistant STEC serogroups (O157, O26, O45, O103, and O111). The efficacy of acidic electrolyzed oxidizing water (AEO), near-neutral electrolyzed oxidizing water, bleach, lactic acid (4% LA), levulinic acid with sodium dodecyl sulfate (LVASDS 2%:0.02%), Birkoside MP-2 (250 ppm) and acetic acid (160 ppm) was evaluated using a pilot size carcass spray-washing cabinet. Samples after treatment were trimmed and enumerated. Sanitizers showing better reduction were combined to form multiple hurdle intervention protocol.

Results: Individual treatment with AEO, LA, and LVASDS showed 1.7, 3.9, and 1.8 log CFU reductions, respectively. Application of multiple hurdle intervention treatment on beef samples inoculated with seven log CFU/cm² resulted in 5.4 and 3.5 log CFU E. coli O157/cm² reductions on fat and lean side of subprimal beef, respectively. Whereas, samples inoculated with a low concentration (five log CFU/cm²) resulted in 3.5 log CFU/cm² reductions on both meat surfaces. NonO157 STEC serogroups E. coli O26, O45, and O103 showed similar reduction trend. However, E. coli O111 was significantly (P<0.05) more resistant and showed reduction in range of 1.9 to 3.7 log CFU/cm².

Significance: The protocol developed in this study can be used for reducing risk of STEC on beef carcass and trims.